$ { \left[\begin{array}{rr}{1} & {0} \\ {-2} & {-1} \\ {-1} & {1}\end{array}\right]+\left[\begin{array}{rr}{3} & {-2} \\ {1} & {1} \\ {2} & {-2}\end{array}\right] = {?} } $
Explanation: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rr}{1}+{3} & {0}+{-2} \\ {-2}+{1} & {-1}+{1} \\ {-1}+{2} & {1}+{-2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{4} & {-2} \\ {-1} & {0} \\ {1} & {-1}\end{array}\right]}$